The invention relates to recuperators primarily for use in gas turbine engines, and more particularly to an end sheet construction for the cores of such recuperators.
The present invention provides a heat exchanger comprising a core including a stacked array of plate-fin cells and a top sheet positioned over the core.
The core is adapted to heat air flowing through the cells with hot gases flowing in-between the cells, and includes a substantially isothermal cool portion into which the flow of air enters the cells and out of which the flow of hot gases exits the core from in-between the cells, a substantially isothermal hot portion into which the flow of hot gases enters the core in-between the cells and out of which the flow of air exits the cells, and a matrix portion in-between the substantially isothermal hot and cool portions.
The air and hot gases flow in counterflow relationship to each other through the matrix portion. The majority of heat transfer between the flows of air and hot gases occurs within the matrix portion, and a temperature gradient is therefore established across the matrix portion.
The top sheet includes first and second ends and a middle portion between the first and second ends. The middle portion includes a window and compliant ligament portions extending alongside the window and interconnecting the first and second ends. The first and second ends of the top sheet are positioned over the isothermal cool and hot portions of the core, respectively, and the middle portion of the top sheet is positioned over the matrix portion of the core. The compliant ligament portions of the top sheet are deflectable in response to the temperature gradient across the matrix portion of the core to reduce strain on and deflection of the first and second ends of the top sheet.